Recovery of zinc.



C. H. FULTON.

RECOVERY 0F ZINC.

C. H. FULTON.

RECOVERY 0F ZINC. APPLICATION FILED JULY I1. Isls.

1 ,21 3, 1 80. Patented J an. 23, 1917.

UNTTED sTATEs PATENT OFFICE.

CHARLES H. FULTON, 0l,` CLEVELAND, OHIOl ASSIGNOR TO DAVID IB. JONES, OF CHICAGO,

ILLINOIS.

lSpecification of Letters Patent.

Application led July 17, 18916. Serial No. 109,724.

To all whom t may concern Be it known that I, CHARLES I-I. FULTON, a citizen of the United States, residing-at Cleveland, in the county of Cuyahoga and State of Ohio, have invented certain new and useful Improvements in the Recovery of Zinc, of which the following is a description, reference bein had to the accompanying drawings, formmg part of this specification.

My invention relates to a novel method of electrically distilling zinc ore, for the recovery of spelter or oxid, andconsists (1) in the formation of the ulverized ore, reducing agent and a suitable' binder into briquets which will maintain their form and volume when subsequently subjected to distillation, (2) preheating said briquets in a reducing atmosphere to drive oii the volatile contents of the binder and\coke the latter and to convert the briquets into conductors of electricity, (3) interposing the ,briquets` as a continuous xed resistance between electrodes in a closed retort furnace and passing through them an electric current of such strength as will cause the briquets to be heated to a distillingtemperature, and (4) recovering the zinc vapors of distillation in the form of spelter or zinc oxid. It

is essential to the practice of my invention that the briquets shall-be of such acomposition and character that they will not break down or disintegrate in the course of the distilling operation, but will preserve their form and volume, so that they will not shrink away from the electrodes or cause arcs due tobad contacts, but will insure a lsteady flow of current and consequently a uniform heatin and distillation. I have described such briquets, of the character which I preferably employ, in my pending appli cation for Letters Patent No. 68,383, filed December 23, 1915. As there described said briquets are composed of the ground andl calcined ore, pulverized coke' and hhard, coal- 'tar pitch, in proportions varying with different ores, as described in said application, but which mav be stated tween and 60% (by welght) of ore, between 30% and 40% (by weight) of coke,

and between 10% and 20% (by. weight) ofpitch. The essential thing in re ect to the" ore and coke is that they shall e of such enerally as beproportions that there will be left, after dis. t1llat1on, a sufficient mass of porous material to maintain the original volume of thel briquet, as explained in my said application, and the essentialv thing in respect to the amount of pitch or other binderis that it shall be suiicient to completely surround the particles of ore and coke with a fllm of blnder, which will unite them together into a coherent mass by its adh'esive action ywhen the briquet is first formed, and which, after the preheating of the briquet' and will permanently-and coking of the binder,

firmly unite the particles of ore and coke by means of the coked residue of the binder leftin the briquet. In making up such briquets the hard coal tar pitch', `if that be the binder employed, is finely ground and mixed with the pulverized ore and coke until a uniform mixture of the three is obtained. The mixture is then heated to the melting point of the pitch, which melts and softens in place and thoroughly coats each article of ore' and coke. The mixture is then formed into bri uets of any desired Shape, but preferably, or the purposes of my present invention, of cyhndrical shape, in suitable molds, in which they are subjected to a high pressure, preferably upward of 500 pounds `to -the square inch, to solidify the mixture and form it into as rm and compact a mass as possible. The briquets are next preheated or dried, for the purpose of drivin ofi the volatile hydrocarbons of the bmder whichvwould tend to dilute the zinc vapors resulting fromdistillation, and converting the binder into coke. This is preferably done by subjecting the briquets,l under reducing or non-oxidizing conditions, to a gradually .rising temperature reaching from 400 Cato I have found'that-the pltch whlch YPatented Jan. 23, 1917.

nely crushed coke, by which'they are com pletely covered and inclosed, or by preheating them in a heating chamber from which oxygen is excluded.

The structure of the briquets produced in the manner above described is that of a large number of ore particles embedded in f a coke matrix, this matrix being made up of the original coke and the coke left by the distillationrof the pitch binder, and are of by the passage of the current through'them,

may be employed in carrying out my invention. In the accompanying drawings I have illustrated one suitable form of such furnace, representing, with some modifications not affecting its general mode of opera- A tion or the describedpractice of my invention, a furnace which I have successfully used' and am now usingin the practice of my invention.

` In said drawings Figure 1 is a view,

vpartly in side elevation and partly in secvertical section, and with the supplyksqf bri-v 3 a sectional planview on theline 3 3 of tion, of the furnace, with thelifting means by which the briquets are lifted into the distillation chamber or retort shown in its lower position, as it would appear either immediatelyv after the distilled briquets have been withdrawn from ysuch chamber or immediately before the undistilled briquets have been raised into it; 'Fig'. 2 is a corresponding view,l showing .all of the furnace excepting the supporting columns in middle quets lifted into. position in the illing chamber Fig. 2- a detail view on anl'enlarged 4scale corresponding to Fig. 2; Fig.

Fig. 2, beingin a plane between the boti tom of the columns of briquets inthe heating chamber and the top of the electrodes upon which they rest, the columns of briquets beingv indicated in dotted lines; Fig. 4 a top plan view of the electrodes resting on the tops of the ,columns of briquets, the view being taken in the vplaneV indicated by the dotted line 4-4 of Fg. 2a; Fig. 5 a top plan view of the supporting' grid or' block, constitutin' the closure for the upper end of the con enser, upon -which the electrodes and columns of briquets are supported ;v Fig. 6 a sectional plan view in the plane indicated lby the dotted line 6--6 of Fig. 2*; and Fig. 7 a detail view of one of the spring pressure devices of Figs. 3 and 6.

The same letters of reference are used to indicate corresponding parts in the several vlews.

Mounted upon a platform 5, Ain this instance consisting ofa square freclay tile' opening 5a to permit the raising and lowering through it of the columns of briquets 23 and the electrodes 25 and 254 at their lower and upper ends, as well as the centralcylindrical upper end of the fireclay tile 24 which constitutes the Iclosure for the upper end of the condenser (hereinafter described) and the support for the columns of briquets andthe electrodes. The platform 5 is further provided beneath its 'central opening 5l above referredto with an annular recess 5* whose upper wall forms an annular downwardly facing. shoulder for contact with the upwardly facing annular shoulder of the tile 24 and the upper end of the cylindrical wall of the 4condenser B. This condenser consists of a cylindrical chamber resting at its open lower end upon .a tile 10 which in turn rests upon a. metal supporting plate 11 secured to and carried by the upper end of the piston 12 ,of a hydraulic lift, composed of ysaid piston 12 and .a cylinder 16 to which water under pressure is, admitted by a pipe v15. The cylinder 16 extends a suiicient distance below the ground or support 33 u on which the-columns 7 rest to accommo ate the'length of the piston 12. The pipe 15 is v provided with an inlet valve 13"and a dis-Vv charge valve 14, forthe admission of water to and itsl release fromthe cylinder 16. At the top of the cylinder 16 the piston 12 is surrounded by a rest block 1 7 seated on the support 33.

In the presentwall of thev condenser B is ycomposedof an outer steel shell 8 immediately inclosing a instance the ycylindrical i cylinder 2 constructed of fire brick and separated from a smaller and thinner cylinder 2'? of a similar character inclosed within it by an annular space 30 filled with powdered graphite for electrically heating the condenser.

tervals around the same, in the present innance at three equidistant points, as shown For the latter purpose there are' interposed in the annular space 30, at in in Figs. 5 and 6, carbon strips 29 extending substantially the vertical length of such annular space and in contact at their lower ends with electrodes 27 hereinafter described.

Located centrally in the condenser B, and resting at their lower ends upon the platform 10, are two integrally formed rightangular cross walls 18, forming four radially projecting vertically extending wings with four quadrants or sectors between them.

Located in these latter Spaces, at intervals in the vertical length of the walls 18, are quadrant-shaped condensing plates 19 composed of fire-brick and resting upon supporting bricks 19a carried by the walls 18. The outer edges of these plates 19 and of their vertical supporting walls 18 are surrounded by an open annular space 22 extending the full length of the condenser B. The plates 19 have their inner corners so shaped or cut away as to provide vertical open spaces between them and the walls 18 at the inner corners of the latter, to permit free vertical passage of the Zinc vapors descending into condenser B from the distilling chamber A above, as hereinafter explained. The walls 18 are further provided with openings 21, to facilitate the free circulation of the zinc vapors within the condenser.

Resting upon the tops of the supporting columns 7 'with interposed angular retaining plates 9 and non-conducting material 3C, is a rectangular platform 6 composed of a reclay tile and having a central circular opening of the vertical passage of the condenser and parts carried by it; while resting upon the top of this platform 6 are cylindrical supporting walls 3a separated by an annular space 3b filled with non-conducting material. The platform 5 which carries the dstilling chamber or retort A rests upon the upper ends of these supporting walls 8a and is thereby indirectly supported upon the platform 6 and columns 7, as before described.

In the present instance 1 have shown twelve vertical columns of cylindrical briquets 23 as constituting a charge for the retort A, and as the furnace shown has been designed for use with a three-phase alternat- -ing current connection of the Y-type the columns of briquets are arranged in siX pairs, for the purpose of passing the current through them in the manner hereinafter eX- plaiued. vThe columns of briquets rest upon the graphite electrodes 25 and 25a, which in turn rest upon the tile-block or grid 24 which constitutes the closure for the upper end of the condenser B. The three electrodes 2 5a (Fig. 3) are each of suitable size and shape to support two columns of briquets and are located at equidistant points around the block 24 adjacent the periphery of its up- Wardly projecting circular central portion,

while the electrode 25 is a three-armed neutral-point electrode, two columns of briquets being supported upon each of its three radial arms, as shown. Current is conveyed to the electrodes 25a by three graphite electrodes 26 adapted to be inserted from the exterior' `of the retort chamber through suitable openings therein immediately above ythe platform 5 and to contact at their inner ends with the electrodes 25a, said contacts being yieldingly maintained by the spring pressure devices 28 best shown in Figs. 3 and 7 and hereinafter described.

.ft the tops of the columns of briquets the adjacent pairs of columns are connected inthe manner shownin Fig. 4 by the electrodes 25', each of which is suitably shaped to rest upon and electrically connect the tops of two adjacent pairs of columns. In Figs. 2 and 3 1 have shown twelve additional briquets restingin pairs upon the tops of the electrodes 25', to serve the purposes of weights to maintain better contact between the electrodes 25 and the tops of the columns of briquets upon which said electrodes rest.

Under the above described construction and arrangement'of parts, if we take, for the purposes of explanation, the current conveyed to the left hand pair of columns of briquets in Fig. 3 by the left hand electrode 26 there shown, the current will pass upward through upper left-hand arm of said electrode in Fig.'

3, thence to the neutral point at the center of said electrode. The passage of che current for the other pairs of columns of briquets is similarly all convergent on the neutral point of vthe electrode 25, which gives the common Y-connection of the alternating three-phase current.

Briquets of the composition and character above described have a specific resistance of about .03 ohms per' cubic inch, and the columns of briquets interposed between the electrodes will have a certain definite resistance, which may be readily calculated by the cross-sections of the briquets, the height and number of the columns,\and the manner of connecting them with each other; and any desired quantity of electric current can be passed through them, dependent upon the voltage impressed upon the electrodes 26. By varying the amount of current sent through the briquets, the speed of distillation may be kept'under perfect control, and

the rate of distillation be varied at will. The

--to supply current-at different voltages. If

[the current is too great or too small, at any given voltage, the voltage at the transformer may be decreased or increased luntil the proper iow--of current is obtained. The

v amount of-` current passed through the briquets is preferably at first relatively small, so that the walls l of the retort A will be heated, -rather gradually to about -tilling temperature.

700 Cl `or 800o C. by radiation from the briquets The current may then be rapidly or grid 24 into the condenserB, The condenser is kept at a temperature between 500 and 650 C., the higher temperature obtaining near the top and the lower near the bottom. The zinc vapor strikes against the condensing plates 1,9, and circulates between I the same and the walls 18, aswell as through the openings 21 and in the annular space 22 surrounding the walls 18. The large surfaces-aorded by these parts and the inv `terior walls 2 of the condenser .serve to Y; rapidly condense the zinc vapor into `liquid I- Y zinc, which collects in the bottom of the condenser The .carbon mon-oxid gas evolved in the distillation of the briquets passes out and burns at the opening 32 in the bottom Y of the condenser; The liquid'zinc is tapped 'of at the tap 31.. When the briquets are 35 Hdying down of the flame at the opening 32,

completely distilled, which is known bythe the 'condenser is lowered by means of the v,hydraulic apparatus into the position shown Vin Fig. 1-, and the briquets then quenchedrapidly with a spray of water and removed fromfthe grid 24, a fresh charge put in their place,l and the condenser again raised into distilling position and the described opera- 't tion repeated.

4The heating of the condenser B, above re- '.ferred to, may be effected by current supplied to the vertical carbon strips 29, through the electrodes 27, which electrodes may be yieidmgly held in piace, with their innerfends in contact with the strips 29, by means of spring-devices 28 similarto those employed for holdingthe electrodes 26 in po sition, as shown in Fig. 6. Referring to vthese spring-devices for holding the electrodes in place, one of those shown in Fig.

3 is valso shown in enlarged sectional detail in Fig. 7, where it willbe seen that Ythe outer surrounding wall la of the retort chamber 'A has seated in it two outwardly pro-v jecting bolts 33 upon kwhich are mounted the spring-devices which operate to press Vthe electrode 26 inward against the electrode 253/ upon which two of the vertical columns of lbriquets within the 'retort A' are supported. A

Mounted upon these bolts 33, with suitable interposed bushings 34 of insulating mate-- rial, is a copper plate 35 to which the conductors 36 conveying the electric current are connected. Fitting against the inner side of the plate 35, with like interposed insulating bushings surrounding the bolts 33,

the outer portion of which is of cup shape and of suitable size to receive and partially inclose the box 38 of the water cooler. Wa-

ter is circulated through the latter by means of inlet and outlet pipes 41 and 42. Coiled springs surrounding the'outer ends of the bolts 33 and confined thereon by uts43 and pressing inward-against the plate 35 serve to press the latter inward and maintain contact between Vthe part 38 of the water cooler and the electrode 26 and between the latter and the electrode 25.

The connection of the supply conductors with the three electrodes 27 and vertical heater strips -29 for heating the' condenser B, as shown in Fig. 6, constitutes the ordinary Vdelta or triangle connection..

I am aware vthat it has been proposed to distil zinc ore in an electric furnace by employing the ore charge itself ,as the resistor between the 'electrodesl of the furnace, but I am not-aware of any instance '1n-which* the ore charge has been made up into briquets of a composition and character which would preserve their form and volume during dis tillation, which is a very greatadvantage and I believe essential to the successful dis- -tillation of zinc ore in this manner. Where the ore charge 1n loose form is employed asI the resistor, the charge changes its form and atmosphere and lexclude foreign gases, for

retort Vand to niaintaina strictly reducing which reasons, I am informed, such'arc furnaces have failed inthe satisfactory con-v densation lof the zinc vapor. l

By forming` the ore charge into briquets of the character 1 have described, and emsistor between the electrodes of the furnace,

the heat is developed uniformly in the charge of ore itself, with no local overheating as in an arc furnace, and the heat is developed where it is absorbed by the reactions involved, Without serious loss by radiation. The furnace may be readily worked as a closed furnace of the retort type, th-e charge being maintained under strictly reducing conditions, With the exclusion of gases except the carbon monoxid generated by the reduction. The closed furnace is very desirable for the subsequent successful condensation of the zinc vapor. I have found it possible to relatively somewhat increase the amount of zinc vapor and decrease the amount of carbon mon-oxid, by heating the briquets to a temperature of about 950J C. and maintaining this temperature for a time, during which some of the zinc oxid is reduced, but the zinc is not kvaporized to any appreciable extent, chieiiy carbon mon-Oxid being liberated and burned at the opening 32. The eect of this is that in the later stages of the distillation the concentration of the zinc vapor may be increased and a better condensation of liquid zinc obtained in the condenser.

While I have described the preheating of A the briquets as a separate and distinct step in my novel process or method of recovering zinc, preferably carried on in a heating chamber separate and apart from the distilling furnace, such preheating of the briqu-ets may nevertheless be effected in the retort of the furnace itself. Under the latter practice, when a charge of briquets has been distilled itis lowered out of the retort in the manner described, the distilled briquets are quenched and removed from the seat 24 and the electrodes 25, a new charge of briquets is put in place and lifted up into the retort while the latter is still white hot.

The stored heat in the retort will be suii` cient to properly preheat the briquets, coking the binder content of them and making them conductors of electricity, after which the current may be turned on and the distilling operation proceded with in the regular way. The volatile matter evolved during the preheating of the briquets in this manner may be permitted to escape at the opening 32, or, if considered undesirable to have it pass through the condenser, a hole maybe provided in the cover 4: of the retort, which may be closed with reclay after the preheating has beeny completed. Where, therefore, the preheating of the briquets is referred to as a separate and distinct step in my novel method, both in the statement of my invention at the beginning of ,this speciiication and in the following claims, it will be understood that such statement and claims contemplate the carrying on 'of such step either in an independent heating cham! ber or in the retort of the distilling furnace in the manner last described above.

Having thus fully described my invention, I

I claim:

l. The herein describedI method of recovering zinc, which consists in (l) mixing the ground and calcined ore with a reducing agent and a binder of such a character and 1n such proportions as will cause briquets formed from such mixture to maintain their form and lvolume during the process of distillation, (2) forming such ore mixture into compact briquets under pressure, (3) preheating such briquets to drive off the volatile contents of the binder and convert the latter into coke, (4) interposing said briquets as a continuous resistor between the electrodes of a closed electric furnace and passing a current of electricity through them to heat them to a distilling temperature, and 5) recovering the zinc from the zinc vapor evolved by the distillation of the briquets.

2. The herein described method of recovering zinc, which consists in (1) mixing the ground and calcined ore with pulveri'zed coke and With a carbonaceous binder such as pitch in such proportions as will cause the briquets formed from such mixture to maintain their form and volume during the process of distillation, (2) forming such ore mixture into compact briquets under pressure, (3) preheating such briquets to drive off the volatile contents of the binder and convert the latter into coke, (4) interposing said briquets as a continuous resistor between the electrodes of a closed electric furnace and passing a current of electricity through them to heat them to a distillng temperature, and (5) recovering the zinc from the zinc vapor evolved by the `distillation of the briquets.

CHARLES H. FULTON. 

